A +20 dBm Highly Efficient Linear Outphasing Class-E PA Without AM/AM and AM/PM Characterization Requirements

Abstract

Outphasing Class-E Power Amplifiers (OEPAs) using isolating power combiners and an inverse cosine signal component separator are inherently linear but suffer from low efficiency at power back-off. For high efficiency both at maximum output power and at power back-off, non-isolating power combiners are required. In this work the linearity of OEPAs using nonisolating power combiners is studied theoretically and validated by measurement of a 1.8GHz 20dBm OEPA implemented in a standard 65nm CMOS technology using an off-chip transmissionline based combiner. The developed theoretical model for the linearity is then employed to define digital pre-distortion (DPD) parameters for the implemented OEPA. Using this theory-based DPD and without any AM/AM and AM/PM characterizations,-31dB RMS EVM level and below-30dB ACLR were measured for a 13.1dBm 6.25MHz 30Mbit/s 7dB PAPR 64QAM signal with 41.8% drain efficiency and 33.6% power added efficiency.